The head of Nomura Holdings Inc., Japan's biggest brokerage, had been itching to shake things up since he began his new job in April.

So when storied Wall Street firm Lehman Brothers Holdings Inc. collapsed just five months later, Kenichi Watanabe pounced.

The firm snapped up Lehman's operations in Asia, Europe and the Middle East for $2 billion in what the 55-year-old president and chief executive describes as a "once-in-a-generation" opportunity. It later added three of Lehman's subsidiaries in India.